1. Field of the Invention
The present invention relates to a structure for stabilizing an object image in an optical system, and more particularly, to the structure for stabilizing the image in the optical system having a compensating lens movable in a surface intersecting an optical axis of the system so as to compensate an image blurred by such as a camera-shake.
2. Description of the Related Art
According to a known structure, a part of lenses, of a photographing optical system mounted in a lens barrel, serving as a lens for compensating an image blurred by such as a camera-shake is moved in a direction perpendicular to the optical axis of the system. Thus, an image shake is compensated or restrained to stabilize an image. Generally, a lens barrel having such a structure is called a shake compensating lens barrel. When a zooming or focusing operation is carried out by the shake compensating lens barrel, it is necessary to move the compensating lens together with other lenses along the optical axis. According to a known shake compensating lens barrel, a mechanism including a motor for perpendicularly driving the compensating lens is mounted on the frame which moves along the optical axis thereby moving the compensating lens therewith for the zooming or focusing so that the mechanism for perpendicularly driving the compensating lens can be adopted in a zooming or focusing mechanism including a driving system which moves the lenses composing the photographing optical system along the optical axis of the system.
The mounting of the compensating lens driving mechanism on the compensating lens moving frame does not unfavorably optically affect the zooming or focusing operation of the photographing optical system, but the load of the driving system for the photographing optical system becomes great because the compensating lens and the compensating lens driving mechanism are moved together by the driving system. In particular, in an automatic focusing camera, the load of a focusing driving motor becomes great, with the result that the response speed of a focusing operation becomes slow.
In the compensating lens driving mechanism of such a shake compensating lens barrel, a gear mechanism such as a reduction gear is included in a driving force transmitting system disposed between the driving motor and the compensating lens. The backlash of each gear of the gear mechanism has an unfavorable influence on the operation accuracy of the compensating lens driving mechanism. Thus, a compensating operation cannot be preferably accomplished.
A small driving load of the movement of the compensating lens along the optical axis means that in a zooming or a focusing operation the movement of the compensating lens is light and the response of the photographing optical system is eventually quick. To reduce the driving load, it is necessary to reduce the weights of the compensating lens unit including the components of the mechanism for perpendicularly driving the compensating lens. For example, plastics are preferably used as the material of various components of the lens unit. However, plastic materials are not so resistant to abrasion. Further, the driving mechanism of the compensating lens has members which repeatedly slide at high speed. If plastic materials are adopted in such members, the members reduce the accuracy of the compensating operation in a short period. Thus, it is hard to adopt plastics as the material of these members.